Heat exchanger

ABSTRACT

A heat exchanger comprising a bundle of substantially parallel pipes, the ends of said pipes presenting a convex configuration at one end of the bundle and a concave configuration at the other end of the bundle, the length and the relative displacement of the pipes in said bundle being such that the total transverse area of the pipes in any transverse plane through said bundle is substantially less than the total projected transverse area of the pipes of the bundle, input header means supplying fluid to one end of the pipes in said bundle, and outlet header means withdrawing fluid from the other end of the pipes in said bundle.

t! o a "l M, Elite tatee att [151 3,638,719

MeGann 1 Feb. 1, 1972 [54] HEAT EXCHANGER 683,267 11/1939 Germany ..158/ 822,759 10/1959 Great Britain ..l65/164 [72] Inventor: Rodney McGann, Northridge, Calif.

[73] Assignee: Texaco, Inc, New York, NY. Emmi'lersamuel Engle Attorney-Stowe" and Stowell [22] Filed: Feb. 20, 1964 21 Appl 34 197 EXEMPLARY CLAIM A heat exchanger comprising a bundle of substantially parallel 52 us. C1 ..l65/164, /267 p p the ends of Said P p Presenting a convex configuration [51] Int. Cl ..F28d 7/04 at one end of e bu d e and a conca e configuration at the [58] Field of Search ..165/ 164, 165, 166, 167, 175, other end of the bundle, h l ng h and h r l iv displace- 165/176, 158, 180, 133, 172; 60/267 ment of the pipes in said bundle being such that the total transverse area of the pipes in any transverse plane through said [56] References Cited bundle is substantially less than the total projected transverse area of the pipes of the bundle, input header means supplying UNITED STATES PATENTS fluid to one end of the pipes in said bundle, and outlet header 2,745,797 5/1956 Long ..l/180 means Withdrawing fluid fmm the other end of the Pipes in 2,817,499 12/1957 Harding et al .....165/180 Said bundle- 2,856,161 10/1958 Flynn ..165/ X 5 Claims, 4 Drawing Figures PATENTED FEB 1m: 3.638.719

INVENTOR.

RODNEY Mc GANN HEATEXCHANGER This invention relates to improvements in heat exchangers and, in particular, to an improved heat exchanger for use in air breathing reaction engines of the type wherein a portion of the energy of the ram air is transferred to the fuel by heat exchange between the ram air and the fuel.

It has been found that by locating a heat exchanger in the air inlet of air breathing reaction engines, the heat exchanger will cool the ingested difiused air so that the engine downstream of the heat exchange will not be subjected to temperatures exceeding, for example, that corresponding to about Mach 3 (about 650 F.) during Mach 8 flight conditions and the airstream having passed the heat exchanger is more easily compressed.

It is, therefore, a principal object of the present invention to provide a single pass, counterflow, high-temperature air cooling heat exchanger having generally low weight and low-frontal area with a minimum of pressure loss.

These and other objects and advantages of the present invention are provided in a heat exchanger including a bundle of substantially parallel pipes, the ends of which present a convex configuration at one end of the bundle and a concave configuration at the other end of the bundle, input header means supplying fluid to one end of the pipes in the bundle and outlet header means withdrawing fluid from the other end of the pipes in the bundle. The invention is also embodied in such a heat exchanger wherein the length and the relative displacement of the pipes in the bundle is such that the total transverse area of the pipes in any transverse plane through the bundle is substantially less than the total projected transverse area of the pipes in the bundle.

The invention will be more fully described in reference to the illustrative embodiments thereof shown in the accompanying drawings wherein:

FIG. 1 is a generally diagrammatic view in partial transverse cross section of an air-breathing reaction propulsion engine employing a ram air heat exchanger constructed in accordance with the teachings of the present invention;

FIG. 2 is a front end view of the structures illustrated in FIG.

FIG. 3 is a schematic section through the heat exchanger illustrated in FIG. 2 illustrating the parallel arrangement of the bundle of heat exchange pipes of the heat exchanger; and

FIG. 4 is an enlarged fragmentary partial sectional view of one heat exchange pipe of the bundle of pipes of the heat exchanger shown in FIGS. 1 and 2 including a portion of its forward and rearward header means.

Referring to the drawings and, in particular, to FIG. 1, generally designates an air-breathing reaction engine of the type wherein a portion of the energy of the ram air entering the forward end of the engine is transferred to the fuel by heat exchange between the ram air and the fuel as disclosed and claimed in, for example, application Ser. No. 324,957, R. L. Wolf and Rodney McGann, Reaction Propulsion Engine and Method of Operation," filed Nov. 20, 1963 and assigned to applicant's assignee.

In general, the reaction engine 10 includes a shell 12 having a forward end 14 and a rearward end 16. The forward end 14 of the shell or casing 12 connects to the inlet duct for ram air, the path of the ram air being indicated by the directional arrows A. In the forward end 14 of the ram air passage is the indirect heat exchange means 18 of the invention. The heat exchange means 18 has the outer surface of the heat exchange elements thereof in contact with the ram air entering the engine while the internal surface of the indirect heat exchange means provides a path for the flow of fuel from the fuel tank 20.

Fuel from the fuel tank 20 is directed by pump 24 through a conduit 22, thence through conduit 26 to a main rear header 28. Fuel, after passing through the heat exchanger 18, is directed therefrom via a forward main header means 30, thence through conduit 32 to a fuel flow regulating mechanism generally designated 34. From the fuel flow regulating mechanism 34 a portion of the fuel is directed to the turbine 36 and a portion of the fuel may be directed to a regenerative heat exchanger 38 positioned in the combustion chamber 40 for the reaction engine and/or a portion may be directly expanded into the combustion chamber via conduit 42. The turbine 36 drives a compressor 44 which compressor compresses air entering the ram air inlet 14 after the air has been cooled in its passage through the heat exchange means 18. The products of combustion of the fuel and the compressed air and any excess fuel or excess air issue fromthe nozzled outlet 16 of the reaction engine.

Now, referring to FIGS. 1 through 4, in the heat exchange means 18 in the illustrated form of the invention, the rear header means 28 is connected to the forward header means 30 by a bundle 50 of heat exchange pipes 52. As illustrated in FIG. 4, the rearward ends 54 of each of the pipes may be constructed of aluminum, the forward portion 56 of the pipes 52 may be constructed of, for example, columbium, while the intermediate section 58 may be constructed of steel. Thus, the single pass counterflow arrangement of the heat exchange tubes permits the use of less exotic materials in the rear or cooler part of the heat exchanger thereby not only reducing the weight of the assembly but also the cost of materials of construction.

The bundle of heat exchange pipes 50 is connected to the rearward header means 28 through a plurality of secondary header pipes 60. Each of the header pipes 60 has one end in fluid communication with the primary header 28 and each of the secondary header pipes 60 spirals generally inwardly and forwardly as more clearly illustrated in FIGS. 1 and 2 of the drawings. The most inner and forward end of each of the secondary header pipes 60 is closed and each of the secondary headers 60 controls the flow of fluid to a plurality of the heat exchange pipes 52 of the bundle of pipes 50. lnterconnecting a plurality of the heat exchange tubes 52 to the generally spiral secondary header pipes 60 has the particular advantage that thermal expansion of the headers will bring about rotation of the segments rather than primarily radial growth, thereby keeping to a minimum the necessity for expansion joints and the like in the system.

A similar arrangement of secondary generally spirally arranged forward headers 62 connect the forward ends of the heat exchange pipes 52 of the bundle of pipes 50 to the forward primary header 30. It will be noted that in the illustrated form of the invention, the spiral array of secondary headers 60 and 62 are so formed that the bundle 50 of substantially parallel heat exchange pipes 52 present a convex configuration at one end of the bundle and a concave configuration at the other or rearward end of the bundle.

It will be appreciated, however, that the concave and convex surfaces need not be segments of spheres but may comprise other conoidal configurations without departing from the scope of the invention. Further, in the illustrated form of the present invention, the radius of curvature, as illustrated in FIG. 3, is greater than the length L of each of the heat exchange pipes 52 by a distance S whereby the total transverse area of the pipes 52 in any transverse plane through the bundle 50 is substantially less than the total projected transverse area of the pipes 52 of the bundle 50. Therefore, the maximum tube blockage to the passage of air thereabout is only a portion of the tube blockage which would result if all of the tubes started in the same transverse plane. This arrangement, however, increases the overall length of the heat exchanger but normally in aircraft installations, the frontal area is substantially more critical than the length of the vehicle. An ideal compromise between the length of the heat exchanger and the total area of tube blockage results when the maximum tube blockage is from about 50 percent to about percent of the blockage which would result from having all of the tubes start in the same plane. A maximum tube blockage of about 70 percent of the blockage resulting from having all of the tubes start in the same plane is preferred.

it will also be noted that the defined results are achievable even though the convex forward end and the concave rearward end of the heat exchange do not define similar surfaces.

lt will be further apparent from the schematic cross section illustrated in FIG. 3 that preferably for equal heat transfer area per square foot of air flow area in, for example, a cylindrical duct that heat exchange tubes 52 should be distributed proportional to the area contained in each segment of the tube bundle. Therefore, as the forward and rearward secondary segments 60 and 62 spiral forwardly and inwardly, the spacing between the pipes on each segment would increase to main tain the preferred uniform or equal transfer area per square foot of flow area in the duct.

Further, as illustrated more clearly in FIG. 4 of the drawings, the forward header means may be provided with a ceramic or other heat resistant shield 64 aerodynamically shaped to minimize turbulence and to present a minimum area to the flow of air and to minimize damage to the heat exchange by the ingestion of harmful objects such as birds.

As illustrated in FIG. 1 of the drawings, the forward primary header 30 is connected to conduit 32 through a slip joint or flexible connector 66; therefore, all axial expansion is taken up in the single joint. it will be appreciated that the forward primary header 30 may be rigidly attached to the vehicle and the rearward primary header 28 may be connected to the conduit 26 through a suitable expansion joint whereby axial expansion would only be in the rearward direction toward the compressor 44 or each header may be connected to its respective pipe by a suitable heat expansion joint. Further, the heat exchanger of the present invention may be readily tailored for a particular reaction engine or vehicle mission by merely increasing or decreasing the axial length of the heat exchanger assembly without changing the fundamental design parameters of the device.

From the foregoing description considered with the illustrated embodiments of the invention, it will be seen that the novel heat exchange fully accomplishes all of the aims and objects hereinbefore set forth.

lclaim:

1. A heat exchange comprising a bundle of substantially parallel pipes, the ends of said pipes presenting a convex configuration at one end of the bundle and a concave configuration at the other end of the bundle, the length and the relative displacement of the pipes in said bundle being such that the total transverse area of the pipes in any transverse plane through said bundle is substantially less than the total projected transverse area of the pipes of the bundle, input header means supplying fluid to one end of the pipes in said bundle, and outlet header means withdrawing fluid from the other end of the pipes in said bundle.

2. The invention defined in claim 1 wherein each of the pipes of said parallel bundle of pipes is the same length.

3. The invention defined in claim 1 wherein each of the pipes of the bundle of pipes is constructed of a plurality of segments difiering in composition with the most heat resistant composition having connection to the outlet header means.

4. A heat exchange comprising a bundle of substantially parallel pipes, the ends of said pipes presenting a convex configuration at one end of the bundle and a concave configuration at the other end of the bundle, the length and the relative displacement of the pipes in said bundle being such that the total transverse area of the pipes in any transverse plane through said bundle is substantially less than the total projected transverse area of the pipes of the bundle, input header means supplying fluid to one end of the pipes in said bundle, outlet header means withdrawing fluid from the other end of the pipes in said bundle, said inlet header means and said outlet header means including a plurality of generally spiral segments connecting opposite ends of a plurality of said pipes of the bundle of pipes.

5. The invention defined in claim 4 wherein said inlet header means is provided with a heat resistant, streamlines coating.

* =i e a 

1. A heat exchange comprising a bundle of substantially parallel pipes, the ends of said pipes presenting a convex configuration at one end of the bundle and a concave configuration at the other end of the bundle, the length and the relative displacement of the pipes in said bundle being such that the total transverse area of the pipes in any transverse plane through said bundle is substantially less than the total projected transverse area of the pipes of the bundle, input header means supplying fluid to one end of the pipes in said bundle, and outlet header means withdrawing fluid from the other end of the pipes in said bundle.
 2. The invention defined in claim 1 wherein each of the pipes of said parallel bundle of pipes is the same length.
 3. The invention defined in claim 1 wherein each of the pipes of the bundle of pipes is constructed of a plurality of segments differing in composition with the most heat resistant composition having connection to the outlet header means.
 4. A heat exchange comprising a bundle of substantially parallel pipes, the ends of said pipes presenting a convex configuration at one end of the bundle and a concave configuration at the other end of the bundle, the length and the relative displacement of the pipes in said bundle being such that the total transverse area of the pipes in any transverse plane through said bundle is substantially less than the total projected transverse area of the pipes of the bundle, input header means supplying fluid to one end of the pipes in said bundle, outlet header means withdrawing fluid from the other end of the pipes in said bundle, said inlet header means and said outlet header means including a plurality of generally spiral segments connecting opposite ends of a plurality of said pipes of the bundle of pipes.
 5. The invention defined in claim 4 wherein said inlet header means is provided with a heat resistant, streamlines coating. 